Professor Squire is a molecular biophysicist who has worked for nearly 40 years in the general area of fibrous protein structure and function, particularly muscle and connective tissue. His main experimental approaches have been: [1] low-angle and high-angle fibre X-ray diffraction, including millisecond time-resolved X-ray diffraction studies of active muscle using synchrotron radiation, and [2] electron microscopy combined with image processing of muscle thin sections and isolated components. He has authored two monographs on muscle contraction, has edited or co-edited five other books on fibrous proteins, and has published over 100 original papers and reviews on muscle and connective tissue Biophysics. His lecture will describe the ultrastructures of striated muscles at the molecular level as far as is known at present and will describe how muscle protein molecules work together to provide a sophisticated method of production and control of muscular force and movement.